MANILA, Philippines — Defense Secretary Gilberto Teodoro Jr. assailed Chinese officials in Seoul after receiving a surprise message from them onstage while mid-answer at a regional defense summit.

Teodoro was taking a question about Chinese gray-zone coercion in the South China Sea at the Seoul Defense Dialogue when a man walked up behind him and left a sheet of paper on his table. Gray-zone tactics are actions that pressure another state without crossing into armed attack.